1. Field of the Invention
The present invention relates to a photoconductive composition and to a highly sensitive electrophotographic light-sensitive material incorporating such a photoconductive composition, more particularly, it is concerned with a colorless or lightly colored photoconductive composition and a colorless or lightly colored electrophotographic light-sensitive material which has high sensitivity and low residual potential.
2. Description of the Prior Art
Organic photosemiconductors have been studied for a long time for their application in the field of electrophotography. In particulars polyvinyl carbazole is described as being photoconductive and used in an electrophotographic material in German Patent Publication No. 106,811 and U.S. Pat. No. 3,037,861. In addition, the aforementioned German Patent Publication discloses that the optical sensitivity of polyvinyl carbazole can be particularly enhanced by the addition of dyes thereof in small amounts. Electrophotographic recording materials having photoconductive coatings of polymerized heterocyclic vinyl compounds such as polyvinyl carbazole and 2,3,7-trinitro-9-fluoroenone in an amount of about 0.49 to 1.23 mol per mol of the .pi.-electron system containing constitutional repeating unit of the photoconductive polymer are described in German Patent Publication No. 1,572,347 and U.S. Pat. No. 3,484,237. In another electrophotographic recording material, which is described in German Patent Application (OLS) No. 1,797,561, the photoconductive layer is formed from a photoconductive composition containing 2,4,7-trinitro-9-fluorenone and polyvinyl carbazole in the equal amount (by weight). The report published by R. M. Scheffelt in IBM Journal of Research and Development, Vol. 15, No. 1, pp. 75-89 (1971) teaches that each of the above recording materials has excellent properties. On the other hand, the report states on page 76 that a large number of substances described as being a sensitizer for polyvinyl carbazole exert a bad influence on optical sensitivity when used in high concentrations. Further, the same report states on page 77 that 2,4,7-trinitro-9-fluorenone is the most useful of substances which have so far been found useful as a sensitizer for polyvinyl carbazole. However, trinitrofluorenone is relatively expensive and is very toxic, i.e., it has a strong carcinogenicity.